In order to drive an alternating current (AC) load such as a motor with a direct current (DC) power source such as a fuel cell, DC-to-AC conversion is generally necessary. If there are multiple DC power sources of different power and DC voltage levels that are to be combined to drive the AC load, then a power sharing system will generally be needed. Parallel connections are often used for the power sharing system since each DC power source can generally operate independently. Power busses are more commonly AC, and since a parallel AC connection requires a common AC voltage, the various DC voltage levels from the multiple DC power sources should be converted to a common AC voltage.
Existing solutions use a custom DC-to-DC converter with its own control loop to condition an output of a single power module (e.g., fuel cell stack). Existing solutions also employ a separate custom DC-to-AC inverter to generate an AC output voltage, and use an additional controller to coordinate the action of the custom DC-to-DC converter and the custom DC-to-AC inverter. If an existing power sharing system consists of multiple DC power sources of different sizes and voltage levels, a custom DC-to-DC converter with its own control loop and a separate custom DC-to-AC inverter is generally used for each DC power source.
Limitations of existing solutions can include reliance on costly custom designed DC-to-DC converter power conditioners and DC-to-AC inverters, and a substantial time that may be required to design them. A complicated architecture may also be difficult to use for power sharing control of multiple DC power sources with different power and voltage levels. Furthermore, existing solutions may not provide a means to readily consolidate sensor data, which is generally necessary for power sharing at different power levels. Existing solutions also may not provide dynamic adjustment of power sharing ratios for each DC power source such that different source power levels can be successfully interfaced.
Therefore, there is a need for low cost power sharing systems that provide simplified architectures for power sharing at different power levels and for dynamic adjustment of power sharing ratios.